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Applied and Environmental Microbiology, November 2003, p. 6644-6649, Vol. 69, No. 11
0099-2240/03/$08.00+0     DOI: 10.1128/AEM.69.11.6644-6649.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Diffusional Properties of Methanogenic Granular Sludge: 1H NMR Characterization

Piet N. L. Lens,1,2* Rakel Gastesi,2,3 Frank Vergeldt,1 Adriaan C. van Aelst,4 Antonio G. Pisabarro,3 and Henk Van As1

Laboratory of Biophysics,1 Subdepartment of Environmental Technology,2 Plant Cell Biology, University of Wageningen, 6700 EV Wageningen, The Netherlands,4 Department of Agrarian Production, Public University of Navarra, Pamplona, Spain3

Received 6 March 2002/ Accepted 17 August 2003

The diffusive properties of anaerobic methanogenic and sulfidogenic aggregates present in wastewater treatment bioreactors were studied using diffusion analysis by relaxation time-separated pulsed-field gradient nuclear magnetic resonance (NMR) spectroscopy and NMR imaging. NMR spectroscopy measurements were performed at 22°C with 10 ml of granular sludge at a magnetic field strength of 0.5 T (20 MHz resonance frequency for protons). Self-diffusion coefficients of H2O in the investigated series of mesophilic aggregates were found to be 51 to 78% lower than the self-diffusion coefficient of free water. Interestingly, self-diffusion coefficients of H2O were independent of the aggregate size for the size fractions investigated. Diffusional transport occurred faster in aggregates growing under nutrient-rich conditions (e.g., the bottom of a reactor) or at high (55°C) temperatures than in aggregates cultivated in nutrient-poor conditions or at low (10°C) temperatures. Exposure of aggregates to 2.5% glutaraldehyde or heat (70 or 90°C for 30 min) modified the diffusional transport up to 20%. In contrast, deactivation of aggregates by HgCl2 did not affect the H2O self-diffusion coefficient in aggregates. Analysis of NMR images of a single aggregate shows that methanogenic aggregates possess a spin-spin relaxation time and self-diffusion coefficient distribution, which are due to both physical (porosity) and chemical (metal sulfide precipitates) factors.

* Corresponding author. Mailing address: Subdepartment of Environmental Technology, University of Wageningen, Bomenweg 2, P.O. Box 8129, 6700 EV Wageningen, The Netherlands. Phone: 31 317 483851. Fax: 31 317 484208. E-mail: piet.lens{at}wur.nl.

Applied and Environmental Microbiology, November 2003, p. 6644-6649, Vol. 69, No. 11
0099-2240/03/$08.00+0     DOI: 10.1128/AEM.69.11.6644-6649.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Osuna, M. B., van Hullebusch, E. D., Zandvoort, M. H., Iza, J., Lens, P. N. L. (2004). Effect of Cobalt Sorption on Metal Fractionation in Anaerobic Granular Sludge. J. Environ. Qual. 33: 1256-1270 [Abstract] [Full Text]  


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